1. Field of the Invention
This invention relates to bearing material and a method of producing same.
2. Description of the Prior Art
The inventor has carried out research on multi-layer bearing material and a method of producing same and have developed inventions disclosed in U.S. patent specification No. 4,189,522 and U.S. patent specification No. 4,121,928 (Japanese Patent Publication No. 2441/80).
The multi-layer bearing material provided by these inventions is produced by supplying powder to a steel strip, pressing the powder and the steel strip by rolls to provide a bond therebetween, and then subjecting the multi-layer material to sintering. The inventions disclosed in these patents involve the use of the art of rolling the powder into a two or three layer composite bearing. It has since been revealed that difficulties are encountered in controlling the thickness of the supplied powder when the methods provided by the patents are used. Also, it has since been revealed that as the thickness of the powder layers increases, cracks are liable to be formed at the end portions of the layers of powder obtained by rolling. Thus when the methods provided by the patents are used difficulties are experienced in producing bearing material of large thickness, and the bearing materials produced by such methods are low in percentage of elongation which greatly affects toughness and fatigue strength of all the mechanical properties essential to bearing material to enable the bearings to give the best performance. The present invention provides a solution to these problems encountered in carrying the methods of the prior art into practice.